Method for thermal sleeve elimination

ABSTRACT

Arrangements and devices for reducing and/or preventing wear of a thermal sleeve in a nuclear reactor are disclosed. Arrangements include a first structure provided on or in one the thermal sleeve and a second structure provided on or in the head penetration adapter. At least a portion of the first structure and at least another portion of the second structure interact to resist, reduce, and/or prevent rotation of the thermal sleeve about its central axis relative to the head penetration adapter. Devices include a base for coupling to a guide tube of the reactor and a plurality of protruding members extending upward from the base. Each member having a portion for engaging a corresponding portion of a guide funnel of the thermal sleeve.

TECHNICAL FIELD

The present disclosure relates generally to methods for eliminatingthermal sleeves in a nuclear reactor and, more particularly, to methodsfor replacing thermal sleeves in a nuclear reactor with extension tubesattached directly to a control rod drive mechanism (CRDM) penetrationhousing of the nuclear reactor.

BACKGROUND

In a nuclear reactor, thermal sleeves serve four purposes. The thermalsleeve protects the rod cluster control assembly (RCCA) drive rod fromthe fluid effects present in the reactor vessel head plenum (e.g., crossflow). The thermal sleeve facilitates hydraulic communication (flow tothe CRDM) during RCCA insertion (control rod drop). The thermal sleeveprovides alignment to the control drive rod for vessel headinstallation. The thermal sleeve also protects the head penetration andCRDM housing from thermal transients of the reactor coolant.

Thermal sleeves include an outside diameter (OD) and an inside diameter(ID) and include flanges. Thermal sleeves are subject to wear at theflanges and the OD/ID. It has been observed that thermal sleeves aresubject to wear between the upper head and the CRDM penetration housingin a nuclear reactor. This wear has been measured using laser metrologyto determine the amount that a particular thermal sleeve has “dropped.”

Thermal sleeve flange and OD/ID wear results in recurring maintenancecosts. Thermal sleeve failure due to OD/ID wear requires costly repairbefore a return to power is possible. Wear predictions throughPressurized Water Reactor Owners Group (PWROG) programs can be used toidentify which sleeves will need eventual intervention. Proactiveelimination of the thermal sleeves can eliminate or greatly delay futurethermal sleeve inspections for any type of wear.

A method for removing a worn thermal sleeve and replacing it with atemporary “compressible thermal sleeve” has been developed. The methoddoes not require removal of the CRDM motor assembly from the top side ofthe reactor head. The method, however, does not address the failuremechanism due to thermal sleeve wear and CRDM penetration housing. Thus,even a compressible thermal sleeve will most likely continue to wearalong with the CRDM penetration housing.

In response to operational experience of thermal sleeve wear at a numberof nuclear plants there is a clear need for eliminating thermal sleevesused in nuclear reactors. Thermal sleeve flange and/or ID/OD wear havebeen identified during inspection of nuclear reactors. Moreover, thereis a need for replacing the thermal sleeves with extension tubesattached directly to the CRDM penetration housing of the nuclearreactor. Accordingly, there is a strong and repeated need for permanentthermal sleeve replacement to remove the need for multiple, variedthermal sleeve inspections over time.

SUMMARY

In one aspect, the present disclosure provides a method for installingan extension tube in a nuclear reactor comprising a control rod drivemechanism (CRDM) housing with a threaded head penetration nozzle and athermal sleeve disposed therein. The method comprises removing thethermal sleeve from the threaded head penetration nozzle and aligning anextension tube with the threaded end of the head penetration nozzle. Theextension tube comprises a threaded end and non-threaded end, thethreaded end sized and configured to threadably couple to the threadedhead penetration nozzle. The method further comprises threading thethreaded end of the extension tube to the threaded end of the threadedhead penetration nozzle, torqueing the extension tube to the threadedend of the threaded head penetration nozzle, gauging the alignment ofthe extension tube relative to the threaded head penetration nozzle,installing retention fillet welds between the extension tube and thethreaded end of the threaded head penetration nozzle, and installing aguide funnel to the non-threaded end of the extension tube.

In one aspect, the present disclosure provides a method for installingan extension tube in a nuclear reactor comprising a control rod drivemechanism (CRDM) housing with a non-threaded head penetration nozzle anda thermal sleeve disposed therein. The method comprises machining thenon-threaded CRDM housing, installing and aligning a threaded adapter tothe machined end of the non-threaded CRDM housing, joining the threadedadapter to the machined end of the non-threaded CRDM housing, machininga bore defined by the non-threaded CRDM housing, machining a boredefined by the threaded adapter, machining an outside diameter of thejoint between the machined end of the non-threaded CRDM housing and thethreaded adapter, installing an extension tube to the threaded adapter,and installing retention fillets welds between the extension tube andthe threaded adapter.

In addition to the foregoing, various other method and/or system and/orprogram product aspects are set forth and described in the teachingssuch as text (e.g., claims and/or detailed description) and/or drawingsof the present disclosure.

The foregoing is a summary and thus may contain simplifications,generalizations, inclusions, and/or omissions of detail; consequently,those skilled in the art will appreciate that the summary isillustrative only and is NOT intended to be in any way limiting. Otheraspects, features, and advantages of the devices and/or processes and/orother subject matter described herein will become apparent in theteachings set forth herein.

In one or more various aspects, related systems include but are notlimited to circuitry and/or programming for effecting herein-referencedmethod aspects; the circuitry and/or programming can be virtually anycombination of hardware, software, and/or firmware configured to affectthe herein-referenced method aspects depending upon the design choicesof the system designer. In addition to the foregoing, various othermethod and/or system aspects are set forth and described in theteachings such as text (e.g., claims and/or detailed description) and/ordrawings of the present disclosure.

Further, it is understood that any one or more of thefollowing-described forms, expressions of forms, examples, can becombined with any one or more of the other following-described forms,expressions of forms, and examples.

The foregoing summary is illustrative only and is not intended to be inanyway limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

FIGURES

The novel features of the described forms are set forth withparticularity in the appended claims. The described forms, however, bothas to organization and methods of operation, may be best understood byreference to the following description, taken in conjunction with theaccompanying drawings in which:

FIG. 1 is a schematic cross-sectional view of an upper portion of aconventional nuclear reactor, according to at least one aspect of thepresent disclosure.

FIG. 2 is a schematic cross-sectional view of a conventional reactorvessel head penetration illustrating a CRDM housing, a head penetrationnozzle, and a thermal sleeve, according to at least one aspect of thepresent disclosure.

FIG. 3 is a section view of a thermal sleeve and CDRM housing in anun-worn condition, according to at least one aspect of the presentdisclosure.

FIG. 4 is a section view of a thermal sleeve and CDRM housing in asubstantially worn condition, according to at least one aspect of thepresent disclosure.

FIG. 5 a section view of a thermal sleeve and CDRM housing in a worncondition to the point of thermal sleeve separation, according to atleast one aspect of the present disclosure.

FIG. 6 illustrate an extension tube that can be installed in a nuclearreactor in place of thermal sleeves, according to at least one aspect ofthe present disclosure.

FIG. 7 illustrates an extension tube that can be installed in thenuclear reactor in place of thermal sleeves, according to at least oneaspect of the present disclosure.

FIG. 8 is a schematic cross-sectional view of an upper portion of aconventional nuclear reactor illustrating a portion of a reactor vesselhead penetrated by a plurality of head penetration nozzles which extenddownward from a CRDM housing, according to at least one aspect of thepresent disclosure.

FIG. 9 is a section view of the threaded penetration adapter shown inFIG. 8 coupled between the extension tube and the head penetrationnozzle, according to at least one aspect of the present disclosure.

FIG. 10 is a section view of a head penetration nozzle with theextension tube, according to at least one aspect of the presentdisclosure.

FIG. 11 is a section view of the head penetration nozzle shown in FIG.10 located through the reactor vessel head, according to at least oneaspect of the present disclosure.

FIG. 12 is a section view of the head penetration nozzle shown in FIGS.10 and 11 with an extension tube attached thereto, according to at leastone aspect of the present disclosure.

FIG. 13 is a perspective view of a compressible guide sleeve, which isreceived in the space defined by the head penetration nozzle shown inFIG. 12, according to at least one aspect of the present disclosure.

FIG. 14 illustrates an extension tube shown in FIGS. 8-10 and 12 with aguide funnel and a threaded penetration adapter, according to at leastone aspect of the present disclosure.

FIG. 15 is a process for removing a thermal sleeve shown in FIGS. 3-5that are need of removal, according to at least one aspect of thepresent disclosure.

FIG. 16 is a process for installing a threaded extension tube, accordingto at least one aspect of the present disclosure.

FIG. 17 illustrates an extension tube comprising a threaded penetrationadapter aligned with a threaded head penetration nozzle extendingthrough a reactor vessel head, according to at least one aspect of thepresent disclosure.

FIG. 18 illustrates the extension tube and threaded head penetrationnozzle shown in FIG. 17 threadably coupled, according to at least oneaspect of the present disclosure.

FIG. 19 illustrates torqueing the extension tube to the head penetrationnozzle shown in FIG. 18 using a torque tool, according to at least oneaspect of the present disclosure.

FIG. 20 illustrates torqueing the extension tube to the head penetrationnozzle shown in FIG. 18 using a torque tool, according to at least oneaspect of the present disclosure.

FIG. 21 is a section view of an extension tube alignment gauging testsetup, according to at least one aspect of the present disclosure.

FIG. 22 is a perspective view of a gauge used in the gauging process ofthe extension tube alignment gauging test setup shown in FIG. 21,according to at least one aspect of the present disclosure.

FIG. 23 is a section view of the alignment of a drive rod relative tothe extension tube, according to at least one aspect of the presentdisclosure.

FIG. 24 illustrates retention fillet welds installed between thethreaded end of the head penetration nozzle shown in FIG. 18 and thethreaded penetration adapter coupled to the extension tube by a weldshown in FIG. 18, according to at least one aspect of the presentdisclosure.

FIG. 25 illustrates a three-leaf compressible flex sections of thecompressible guide sleeve shown in FIG. 13 in a compressed configurationto contract flanges of the compressible flex sections to a size suitablefor introducing into the guide funnel, according to at least one aspectof the present disclosure.

FIG. 26 illustrates a compression tool that may be employed to compressthe compressible guide sleeve shown in FIG. 25 prior to inserting thecompressible guide sleeve into the guide nozzle, according to at leastone aspect of the present disclosure.

FIG. 27 illustrates the compressible guide sleeve shown in FIG. 25 inits compressed configuration inserted through the head penetrationnozzle and the CRDM head adapter, according to at least one aspect ofthe present disclosure.

FIG. 28 illustrates the compressible flex sections of the compressibleguide sleeve shown in FIG. 27 released such that the flanges of thecompressible flex sections engage the counterbore ledge defined withinthe CRDM head adapter section of the head penetration nozzle, accordingto at least one aspect of the present disclosure.

FIG. 29 illustrates the compressible guide sleeve shown in FIG. 28 inits final installed state, according to at least one aspect of thepresent disclosure.

FIG. 30 is a section view of the reactor vessel head illustrating theextension tube coupled to the head penetration nozzle installed insidethe reactor vessel head, according to at least one aspect of the presentdisclosure.

FIG. 31 is a detailed view of the installed extension tube coupled tothe head penetration nozzle shown in FIG. 30 showing the extension tuberetention welds, according to at least one aspect of the presentdisclosure.

FIG. 32 is a section view of the extension tube coupled to the headpenetration nozzle installed inside the reactor vessel head shown inFIG. 31, according to at least one aspect of the present disclosure.

FIG. 33 is an elevation view of the extension tube coupled to the headpenetration nozzle installed inside the reactor vessel head shown inFIG. 32, according to at least one aspect of the present disclosure.

FIG. 34 illustrates a head penetration nozzle with threads that are notusable, due to wear, damage, or sizing mismatch, according to at leastone aspect of the present disclosure.

FIG. 35 is a section view of the head penetration nozzle shown in FIG.34, according to at least one aspect of the present disclosure.

FIG. 36 is a process for installing an extension tube on a non-threadedCRDM housings, according to at least one aspect of the presentdisclosure.

FIG. 37 is a section view of a non-threaded CRDM housing beforemachining, according to at least one aspect of the present disclosure.

FIG. 38 is a section view of the non-threaded CRDM housing shown infFIG. 37 after machining, according to at least one aspect of the presentdisclosure.

FIG. 39 is a detail view of the section view of the non-threaded CRDMhousing shown in FIG. 38, according to at least one aspect of thepresent disclosure.

FIG. 40 illustrates a threaded adapter comprising male threads sized andconfigured to receive female threads of the extension tube shown in FIG.14 and a non-threaded end configured to abut the machined end face ofthe non-threaded CRDM housing shown in FIGS. 38-39, according to atleast one aspect of the present disclosure.

FIG. 41 illustrates a gap defined between the machined end face of thenon-threaded CRDM housing and the non-threaded end of the threadedadapter shown in FIGS. 38-40, according to at least one aspect of thepresent disclosure.

FIG. 42 illustrates the threaded adapter and the non-threaded CRDMhousing shown in FIG. 41 in a joined configuration, according to atleast one aspect of the present disclosure.

FIG. 43 illustrates machined bores defined by the non-threaded CRDMhousing and the threaded adapter shown in FIG. 42, according to at leastone aspect of the present disclosure.

FIG. 44 illustrates a machined/ground OD of the joint shown in FIGS.42-43, according to at least one aspect of the present disclosure.

FIG. 45 illustrates the joined threaded adapter and non-threaded CRDMhousing shown in FIGS. 38-44 installed below the reactor vessel head andready to receive the extension tube, according to at least one aspect ofthe present disclosure.

FIG. 46 illustrates the joined threaded adapter and non-threaded CRDMhousing shown in FIGS. 38-45 installed below the reactor vessel head andready to receive the extension tube, according to at least one aspect ofthe present disclosure

FIG. 47 illustrates the threaded adapter of the extension tube installedon the threaded adapter attached to the non-threaded CRDM housing asshown in FIGS. 38-46 from below the reactor vessel head, according to atleast one aspect of the present disclosure.

FIG. 48 illustrates retention fillet welds between the threaded adapterof the extension tube and the threaded adapter of the non-threaded CRDMhousing shown in FIGS. 38-47, according to at least one aspect of thepresent disclosure.

DESCRIPTION

This application is related to PCT/US2020/019116, Attorney Docket No.200457PCT, filed on Feb. 20, 2020, titled ANTI-ROTATION ARRANGEMENTS FORTHERMAL SLEEVES, which is herein incorporated by reference in itsentirety.

Before explaining various aspects of methods for eliminating thermalsleeves in nuclear reactors, or more particularly, methods for replacingthe thermal sleeves with extension tubes which attach directly tocontrol rod drive mechanism (CRDM) penetration housings of the nuclearreactor in detail, it should be noted that the illustrative aspects arenot limited in application or use to the details of construction andarrangement of parts illustrated in the accompanying drawings anddescription. The illustrative aspects may be implemented or incorporatedin other aspects, variations and modifications, and may be practiced orcarried out in various ways. Further, unless otherwise indicated, theterms and expressions utilized herein have been chosen for the purposeof describing the illustrative aspects for the convenience of the readerand are not for the purpose of limitation thereof.

Further, it is understood that any one or more of thefollowing-described forms, expressions of forms, examples, can becombined with any one or more of the other following-described forms,expressions of forms, and examples.

In one aspect, the present disclosure is directed, as stated above, tomethods for eliminating thermal sleeves in nuclear reactors. In anotheraspect, the present disclosure is directed to methods for replacing thethermal sleeves with extension tubes which attach directly to CRDMpenetration housings of the nuclear reactor. In one aspect, the thermalsleeve can be removed from underneath the reactor vessel closure head(RVCH) using exiting equipment and processes for thermal sleeve removal.An extension tube, which attaches directly to the CRDM penetrationhousing, is installed. In accordance with one aspect, there are two maincomponents required to eliminate a thermal sleeve. First is theextension tube and second is the upper guide sleeve. The purpose of theupper guide sleeve is to provide the final guidance for the drive rodinto the CRDM through the latch stop plate.

Generally speaking, there are two styles of CRDM penetrationhousings—threaded and non-threaded. Threaded penetrations have a 3¾″-8UN-2A thread. Non-threaded penetrations have a bare tubular end withradii on both the OD and ID to face transitions.

For threaded penetrations, an extension tube may be manufactured to aspecific length which would set a funnel height at the same elevation asexisting thermal sleeves when threaded on and tightened. Fornon-threaded penetrations, a penetration nozzle may be welded on to thepenetration which would then provide the proper male thread forattaching the extension tube.

A special Compressible Guide Sleeve (CGS) has been designed to providethe same functions that the guide sleeve does on replacement RVCHs andAP1000 pressurized water reactors, for example. The CGS can be installedfrom underneath the RVCH, along with the extension tube. The presentdisclosure provides a new and innovative process of retrofitting anextension tube onto an in-service RVCH.

Thermal sleeves that exhibit flange and/or ID/OD wear are suitablecandidates for elimination and replacement with extension tubes toeliminate recurring maintenance costs and failures which require costlyrepairs before a return to power is possible. Wear predictions throughPWROG programs can be used to identify which thermal sleeves will needeventual intervention. Proactive elimination combined with engineeringjustification can eliminate or greatly delay future thermal sleeveinspections for a many types of wear.

FIG. 1 is a schematic cross-sectional view of an upper portion of aconventional nuclear reactor 2 illustrating a portion of a reactorvessel 4 penetrated by a plurality of head penetration nozzles 6 whichextend downward from a CRDM housing 8. FIG. 2 is a schematiccross-sectional view of a conventional reactor vessel head penetrationillustrating a CRDM housing 8, a head penetration nozzle 6, and athermal sleeve 10. Continuing to refer to FIG. 1, as well as to thesectional view of FIG. 2, a thermal sleeve 10 including a guide funnel12 is positioned within each head penetration nozzle 6 beneath each CRDMhousing 8 such that each guide funnel 12 is positioned directly above,and spaced a distance from, a corresponding guide tube 14 extending froman upper support plate 16 within reactor vessel 4. The thermal sleeve 10is housed within the head penetration nozzle 6 within the reactor vessel4 except within region 15 (FIG. 2) where the thermal sleeve 10 isexposed to the reactor coolant.

The current belief is that wear of thermal sleeve 10 and headpenetration nozzle 6 in region 13 illustrated in FIGS. 1 and 2 resultsfrom rotation of the thermal sleeve 10 within the head penetrationnozzle 6 about a central axis 18 of the thermal sleeve 10. It isbelieved that vortices in the reactor coolant flowing within the reactorvessel 4 come into contact with the thermal sleeve 10 (i.e., in region15) causing the thermal sleeve 10 to rotate about its central axis 18relative to the head penetration nozzle 6.

The present disclosure provides methods for eliminating thermal sleeves10 in a nuclear reactor 2 and, more particularly, methods for replacingthermal sleeves 10 in a nuclear reactor 2 with extension tubes attacheddirectly to a CRDM penetration housing 6 of the nuclear reactor 2. Thesemethods squarely fulfill the strong and repeated need for permanentthermal sleeve 10 replacement to remove the need for multiple, variedthermal sleeve 10 inspections over time.

FIG. 3 is a section view 100 of a thermal sleeve 110 and a CDRM housing108 in an un-worn condition. The thermal sleeve 110 includes a flange112 defines an outside diameter 114 (OD) and an inside diameter 116 (ID)that are subject to wear. The thermal sleeve 110 is subject to wearbetween the upper head and the CRDM penetration housing 108 in a nuclearreactor.

FIG. 4 is a section view 120 of the thermal sleeve 110 and the CDRMhousing 108 in a substantially worn condition. As discussed above, thethermal sleeve 110 shows substantial wear at the flange 112 and the OD114 and ID 116. This wear my be manifested by a drop of the thermalsleeve 110.

FIG. 5 is a section view 140 of the thermal sleeve 110 and the CDRMhousing in a worn condition to the point of thermal sleeve 110separation. As shown, the thermal sleeve 110 has developed a crack 118resulting in the separation of the thermal sleeve 110. The section view140 also shows additional wear of the flange 112, OD 114, and ID 116relative to the section view 120 shown in FIG. 4.

With reference to FIGS. 1-5, extension tubes can be retrofitted in avariety of reactor vessel 4 (FIG. 1) heads which currently have thermalsleeves 10 (FIGS. 1-2), 110 (FIGS. 3-5) installed. Typical CRDMpenetration designs have either “threaded” or “non-threaded” endsprotruding through the reactor vessel 4 head. With reference also toFIG. 6, an extension tube 200 that can be installed in the nuclearreactor 4 in place of thermal sleeves 10, 110 is shown. The extensiontube 200 comprises a substantially cylindrical body 202 and a threadedend 204 that would protrude through the reactor vessel 4 head onceinstalled and threadably couple to threaded penetration nozzle. FIG. 7illustrates an extension tube 240 that can be installed in the nuclearreactor 4 in place of thermal sleeves 10, 110. The extension tube 240comprises a substantially cylindrical body 242 and a non-threaded end244 that would protrude through the reactor vessel 4 head once installedand couple to a non-threaded penetration nozzle by a suitable weld, forexample.

FIG. 8 is a schematic cross-sectional view of an upper portion of aconventional nuclear reactor 302 illustrating a portion of a reactorvessel head 304 penetrated by a plurality of head penetration nozzles306 which extend downward from a CRDM housing 308. An extension tube 310is coupled to the distal end 314 of the head penetration nozzle 306. Thedistal end 316 of the extension tube includes a guide funnel 312. Thehead penetration nozzles 306 include a compressible guide sleeve 318. Athreaded penetration adapter 320 is coupled between the extension tube310 and the head penetration nozzle 306. In one aspect, the threadedpenetration adapter 320 is employed for non-threaded penetration nozzles306 in order to facilitate the installation of the extension tube 310 ona non-threaded head penetration nozzle 306. The threaded penetrationadapter 320 is welded to the end of the non-threaded head penetrationnozzle 306. Compressible guide sleeves 318 are further described incommonly owned patent application number PCT/US2019/015797, filed Jan.30, 2019, titled THERMAL SLEEVE, which is herein incorporated byreference in its entirety.

FIG. 9 is a section view of the threaded penetration adapter 320 coupledbetween the extension tube 310 and the head penetration nozzle 306. Thetreaded penetration adapter 320 includes a body 322 with an upper endadapted and configured to couple to the non-threaded end of the headpenetration nozzle 306 and a lower end adapted and configured to coupleto the extension tube 310. In one aspect, the upper end of the body 322of the threaded penetration adapter 320 may be welded to thenon-threaded head penetration nozzle 306 at connection 324 and the lowerend of the threaded adapter body 322 may be welded to the extension tube310 at connection 326. In one aspect, the connection 326 is a bimetallicweld in the extension tube 310 to transition to steel. In variousaspects, the threaded penetration adapter 320 may include threads tothreadably couple to the non-threaded head penetration nozzle 306 and/orthe extension tube 310, for example.

FIG. 10 is a section view of a head penetration nozzle 306 with theextension tube 310. The head penetration nozzle 306 extends downwardfrom a latch housing 336 and penetrates the reactor vessel head 304. Thelatch housing 336 contains a CRDM motor 330 and a compressible guidesleeve 332. The latch housing 336 is coupled to the head penetrationnozzle 306 via a bimetallic weld 334. The head penetration nozzle 306 iscoupled to an extension tube 310 within the reactor vessel head 304through a threaded penetration adapter 320. The extension tube 310 iscoupled to a guide funnel 312. As shown in FIG. 10, the thermal sleevein the head penetration nozzle 306 has been replaced by the extensiontube 310.

FIG. 11 is a section view of the head penetration nozzle 306 locatedthrough the reactor vessel head 304. The end of the head penetrationnozzle outside the reactor vessel head 304 comprises a CRDM head adapter337. The head penetration nozzle 306 defines a space 338, which normallycontains a thermal sleeve that is notably missing.

FIG. 12 is a section view of the head penetration nozzle 306 with theextension tube 310. The head penetration nozzle 306 is coupled to theextension tube 310 via an optional threaded penetration adapter 320. Thecompressible guide sleeve 332, shown in detail in FIG. 14, is normallycontained within a space 340 defined by the head penetration nozzle 306.

FIG. 13 is a perspective view of a compressible guide sleeve 332, whichis received in the space 340 defined by the head penetration nozzle 306,as shown in FIG. 12. The compressible guide sleeve 332 comprises athree-leaf compressible flex section 342 for compressibility andstiffness. In various aspects, the compressible guide sleeve maycomprise at least two and more than three compressible sleeves. Each ofthe leaf compressible flex sections 342 includes a flange 344 that ispositioned within the CRDM housing 308. The compressible guide sleeve332 is installed into the CRDM penetration to facilitate drive rodguidance into the latch housing 336 (FIG. 10). The bottom end of thecompressible guide sleeve 332 comprises an alignment feature 346.Existing thermal sleeve elimination modifications in new RVCHs employ asmaller guide sleeve similar to a truncated thermal sleeve. The purposeof the guide sleeve is to provide guidance for the drive rod into theCRDM latch assembly. The compressible guide sleeve 332 accomplishes thesame function as the guide sleeve and is installed from underneath thereactor vessel head 304 (FIGS. 8-12), after the extension tube 310 hasbeen attached to the head penetration nozzle 306. While the design ofthe compressible guide sleeve 332 allows for it to be flexible enough tobe installed through the CRDM penetration, it is also stiff/rigid enoughthat it requires a specialized fixture to compress the compressibleguide sleeve 332 prior to installation. This stiffness is sufficient forit to remain in place during all of a nuclear plant's design basisconditions.

The entire extension tube 310 installation process occurs underneath theRVCH and requires no modifications or removals of the CRDM and requiresno modifications to the upper internal components. Under-the-headinstallation processes are known and have been developed by the owner ofthe present application. The replacement of the thermal sleeve with theentire extension tube 310 eliminates all future thermal sleeve wear atthe installation location. The extension tube 310 requires noinspections for wear throughout its life.

FIG. 14 illustrates an extension tube 310 with a guide funnel 312 and athreaded penetration adapter 320. In one aspect, the guide funnel 312 iscollapsible and is configured to fail before CRDM or fuel damage canoccur in the event of misalignment during head installation. In oneaspect, the threaded penetration adapter 320 includes a threaded endwith female threads 348 to threadably couple to male threads 349 (FIG.17) of the head penetration nozzle 306 (FIGS. 8-13). During the thermalsleeve replacement process, retention fillet welds 352 are providedbetween the threaded penetration adapter 320 and the head penetrationnozzle 306 to stabilize the connection. The threaded penetration adapter320 is coupled to the extension tube 310 by a weld 354. The extensiontube 310 is coupled to the guide funnel 312 by retention fillet welds356.

FIG. 15 is a process 400 for removing a thermal sleeve in need ofremoval. The process 400 will now be described with reference to FIGS.1-5 and 15. The thermal sleeve 10 (FIGS. 1-2), 110 (FIGS. 3-5) in needof removal is identified 402. The ID of the thermal sleeve 10, 110 isflapped and cleaned 404. The electrical discharging machining (EDM) headis installed 406 on one section of the thermal sleeve 10, 110 and the aseries of cuts is performed. Once the series of cuts is completed, thethermal sleeve 10, 110 is removed 408 and the head penetration nozzle306 is cleaned and inspected 410. The thermal sleeve 10, 110 removal isnow complete 412.

FIG. 16 is a process 440 for installing a threaded extension tube. Theprocess 400 will now be described with reference to FIGS. 1-5, 8-14, and16. Once the thermal sleeve 10, 110 is removed 442 the threadedextension tube 310 is installed 444. The extension tube 310 is torqued446 to the head penetration nozzle 306 using a torque tool. Thealignment of the extension tube 310 is gauged 448. Retention filletwelds 352 are installed 450. A compressible guide sleeve 332 isinstalled 452 and the alignment of the extension tube 310 is finallygauged 454. The installation is now complete and the extension tube 310is in its final installed arrangement 456. Details of the extension tubeinstallation process 440 will now be described in more detail.

Still with reference to FIG. 16, FIGS. 17 and 18 illustrate the processstep of installing 444 the threaded extension tube 310. As shown in FIG.17, the extension tube 310 comprising a threaded penetration adapter 320is aligned with a threaded head penetration nozzle 306 extending throughthe reactor vessel head 304. The threaded head penetration nozzle 306comprises a threaded end 307 with male threads 349 configured tothreadably couple the female threads 348 of the threaded end of thethreaded penetration adapter 320. As previously discussed, the threadedpenetration adapter 320 is coupled to the extension tube 310 by a weld354. As shown in FIG. 18, the female threads 348 of the threaded end ofthe threaded penetration adapter 320 is threadably coupled to the malethreads 349 of the threaded end 307 of the threaded penetration adapter320.

Still with reference to FIGS. 16-18, FIGS. 19 and 20 illustratetorqueing 446 the extension tube 310 to the head penetration nozzle 306using a torque tool 500.

Still with reference to FIGS. 16-20, FIGS. 21-23 illustrates the processof gauging 448 the extension tube 310 alignment after it has beenproperly torqued 446 to the head penetration nozzle 306, where FIG. 21is a section view 520 of an extension tube 310 alignment gauging test,FIG. 22 is a perspective view of a gauge 522 used in the gauging 448process, and FIG. 23 is a section view of the alignment of a drive rod530 relative to the extension tube 310. The gauge 522 is inserted intothe guide funnel 312, through the extension tube 310, the headpenetration nozzle 306, and into the CRDM housing 308. The gauge 522 isrotated to fit into the guide funnel 312. The alignment of the extensiontube 310 is measured relative to a nominal centerline with a maximumoffset permitted from the nominal centerline. Datum A is measured at apoint along the extension tube 310 and at a first radial offset 524extending radially from the gauge 522 located at the end of theextension tube 310 near the guide tube 312, a second radial offset 526located within the head penetration nozzle 306 just outside the reactorvessel head 304, and a third radial offset 528 located inside the CRDMhousing 308. The amount of shift relative to datum A is determined ateach radial offset 524, 256, 528 location. In FIG. 23, the alignment ofa drive rod 532 is shown relative to the inlet of the guide funnel 312.

Once the gauging 448 of the extension tube 310 alignment, the retentionfillet welds 352 are installed 450. Still with reference to FIGS. 16-23,FIG. 24 illustrates the retention fillet welds 352 installed 450 betweenthe threaded end 307 of the head penetration nozzle 306 and the threadedpenetration adapter 320 coupled to the extension tube 310 by a weld 354.

Following the installation 450 of the retention fillet welds 352, thecompressible guide sleeve 332 is installed 452. Still with reference toFIGS. 16-24, FIGS. 25-29 illustrate the process of installing 452 thecompressible guide sleeve 332. As shown in FIG. 25, the three-leafcompressible flex sections 342 of the compressible guide sleeve 332 arecompressed to contract the flanges 344 of the compressible flex sections342 to a size suitable for introducing into the guide funnel 312. FIG.26 illustrates a compression tool 536 that may be employed to compressthe compressible guide sleeve 332 prior to inserting the compressibleguide sleeve 332 into the guide nozzle 312. FIG. 27 illustrates thecompressible guide sleeve 332 in its compressed configuration insertedthrough the head penetration nozzle 306 and the CRDM head adapter 337such that the flanges 344 of the compressible flex sections 342 arepositioned just above a counterbore ledge 536 defined within the CRDMhead adapter 337 section of the head penetration nozzle 306. In FIG. 28the compressible flex sections 342 of the compressible guide sleeve 332are released such that the flanges 344 of the compressible flex sections342 engage the counterbore ledge 536 defined within the CRDM headadapter 337 section of the head penetration nozzle 306. The counterboreledge 534 retains the compressible guide sleeve 332 within the CRDM headadapter 337 section of the head penetration nozzle 306. FIG. 29illustrates the compressible guide sleeve 332 in its final installedstate. A final gauging 454 of the extension tube 310 can now beperformed.

Still with reference to FIGS. 16-29, FIGS. 30-33 illustrate the finalinstalled arrangement 456 of the extension tube 310. FIG. 30 is asection view of the reactor vessel head 304 illustrating the extensiontube 310 coupled to the head penetration nozzle 306 installed inside thereactor vessel head 304. FIG. 31 is a detailed view of the installedextension tube 310 coupled to the head penetration nozzle 306 showingthe extension tube retention welds 352. FIG. 32 is a section view of theextension tube 310 coupled to the head penetration nozzle 306 installedinside the reactor vessel head 304. FIG. 33 is an elevation view of theextension tube 310 coupled to the head penetration nozzle 306 installedinside the reactor vessel head 304.

FIG. 34 illustrates a head penetration nozzle 306 with threads 552 thatare not usable, due to wear, damage, or sizing mismatch. FIG. 35 is asection view of the head penetration 306 nozzle shown in FIG. 34. Withreference now to FIGS. 17, 34, and 35, if the male threads 349 on thethreaded end 307 of the CRDM head penetration nozzle 306 are not usable,due to wear, damage, or sizing mismatch, in one aspect, a threadedadapter 550 may be employed as a contingency. The threaded adapter 550is welded 554 below the male threads 349 of the head penetration nozzle310. The threaded adapter 550 includes male threads 552 suitable forthreadably coupling the female thread 348 on the threaded adapter 320 ofthe extension tube 310.

The installation of an extension tube 310 in the field becomes morecomplicated at nuclear plants without CRDM housings comprising threadedhead penetration nozzles 306. Additional field machining would berequired to prepare the non-threaded CRDM housing for welding, as wellas perform post-welding cleanup. Design of the extension tube 310remains common between threaded and non-threaded CRDM housings. Aprocess for installing an extension tube 310 on a non-threaded CRDMhousing is described hereinbelow.

FIG. 36 is a process 600 for installing an extension tube on anon-threaded CRDM housings. With reference also to FIGS. 37-39, theprocess 600 begins by machining 602 a non-threaded CRDM housing 650. Inother words, the CRDM housing 650 does not include a threaded headpenetration nozzle with a threaded end 307 with male threads 349 asdescribed with reference to FIGS. 3-35. FIG. 37 is a section view of anon-threaded CRDM housing 650 before machining. The machining 602 stepinvolves preparing the face 652 (FIG. 37, pre-machining) of thenon-threaded CRDM housing 650 geometry for machine welding andturning-back the ID bore 654 of the non-threaded CRDM housing 650. FIG.38 is a section view of the non-threaded CRDM housing 650 aftermachining 602. FIG. 39 is a detail view of the section view of thenon-threaded CRDM housing shown in FIG. 38. As shown in FIGS. 38 and 39,the face 656 (post-machining) of the non-threaded CRDM housing 650 ismachined back to remove the radii and install the prep weld. FIG. 39shows a detailed view of the machined face 656 of the non-threaded CRDMhousing 650.

FIG. 41 illustrates a gap 668 defined between the machined end face 656of the non-threaded CRDM housing 650 and the non-threaded end 654 of thethreaded adapter 660. With continued reference to FIGS. 36-39 and withreference also to FIGS. 14 and 40-41, the next step in the process 600is installing and aligning 604 a threaded adapter 660 to the machinednon-threaded CRDM housing 650. As shown in FIG. 40, the threaded adapter660 comprises male threads 662 sized and configured to receive thefemale threads 348 of the extension tube 310 (See FIG. 14, for example)and a non-threaded end 664 configured to abut the machined end face 656of the non-threaded CRDM housing 650. The threaded adapter 660 alsodefines a bore 670. As shown in FIG. 41, a gap 668 is defined betweenthe machined end face 656 of the non-threaded CRDM housing 650 and thenon-threaded end of the threaded adapter 650.

FIG. 42 illustrates the threaded adapter 660 joined to the non-threadedCRDM housing 650. With continued reference to FIGS. 36-41, and withreference also to FIG. 42, the next step in the process 600 is joining606 the threaded adapter 660 to the non-threaded CRDM housing 650. Inone aspect, the threaded adapter 660 is joined 606 to the CRDM housingby the a penetration welding technique to form a joint 672. In oneaspect, the threaded adapter 660 may be joined 606 to the non-threadedCRDM housing 650 by a full penetration weld that joins 606 the threadedadapter 660 to the non-threaded CRDM housing 650 with no gaps in betweenthe filler material and the roots of the joint 672. In one aspect, thethreaded adapter 660 may be welded to the non-threaded CRDM housing 650may be performed using a specialized semi-automatic gas tungsten arcwelding (GTAW) weld head, for example.

FIG. 43 illustrates machined bores 654, 670 defined by the non-threadedCRDM housing and the threaded adapter. With continued reference to FIGS.36-42, and with reference also to FIG. 43, the next step in the process600 is machining 608 the bore 670 defined by the threaded adapter 660and/or the bore 654 defined by the non-threaded CRDM housing 650. Thisstep removes an integral backing ring/alignment ring.

FIG. 44 illustrates a machined/ground OD 674 of the joint 672. Withcontinued reference to FIGS. 36-43, and with reference also to FIG. 44,the next step in the process 600 is machining/grinding 610 the OD 674 ofthe joint 672, such as the penetration weld cap, for inspections. FIGS.45 and 46 show the threaded adapter 660 attached to the non-threadedCRDM housing 650 installed below the reactor vessel head 304 and readyto receive the extension tube 310.

FIG. 47 illustrates the threaded adapter 320 of the extension tube 310installed on the threaded adapter attached to the non-threaded CRDMhousing from below the reactor vessel head 304. With continued referenceto FIGS. 36-46, and with reference also to FIGS. 14 and 47, the nextstep in the process 600 is installing the threaded adapter 320 of theextension tube 310 on the threaded adapter 660 attached to thenon-threaded CRDM housing from below the reactor vessel head 304. Thisstep includes threading and torqueing the extension tube 310 on thethreaded adapter 660 in manner similar to that described above withreference to 17-20.

FIG. 48 illustrates retention fillet welds 674 between the threadedadapter 320 of the extension tube 310 and the threaded adapter 660 ofthe non-threaded CRDM housing 650. With continued reference to FIGS.36-47, and with reference also to FIGS. 14 and 48, the next step in theprocess 600 is installing 614 retention fillet welds 674. The process600 may comprise installing a guide funnel 312 as described above withreference to 8-14, for example. The process 600 may further comprisegauging the alignment of the extension tube using the same processdescribed above with reference to FIGS. 21-23, for example. The process600 may further comprise installing a compressible guide sleeve 332using the same process described above with reference to FIGS. 25-29,for example.

Although certain aspects have been illustrated and described herein forpurposes of description, a wide variety of alternate and/or equivalentaspects or implementations calculated to achieve the same purposes maybe substituted for the aspects shown and described without departingfrom the scope of the present disclosure. This application is intendedto cover any adaptations or variations of the embodiments discussedherein.

Examples of the methods and/or systems of various aspects of the presentdisclosure are provided below. An aspect of the methods and/or systemsmay include any one or more than one, and any combination of, theexamples described below.

Example 1

A method for installing an extension tube in a nuclear reactorcomprising a control rod drive mechanism (CRDM) housing with a threadedhead penetration nozzle and a thermal sleeve disposed therein. Themethod comprises removing the thermal sleeve from the threaded headpenetration nozzle and aligning an extension tube with the threaded endof the head penetration nozzle. The extension tube comprises a threadedend and non-threaded end, the threaded end sized and configured tothreadably couple to the threaded head penetration nozzle. The methodfurther comprises threading the threaded end of the extension tube tothe threaded end of the threaded head penetration nozzle, torqueing theextension tube to the threaded end of the threaded head penetrationnozzle, gauging the alignment of the extension tube relative to thethreaded head penetration nozzle, installing retention fillet weldsbetween the extension tube and the threaded end of the threaded headpenetration nozzle, and installing a guide funnel to the non-threadedend of the extension tube.

Example 2

The method of Example 1, comprising installing a compressible guidesleeve to the CRDM housing.

Example 3

The method of Example 2, wherein installing the compressible guidesleeve to the CRDM housing comprises compressing the compressible guidesleeve, and inserting the compressed guide sleeve into the guide funnel,through the extension tube, the head penetration nozzle, and the CRDMhousing. Installing the compressible guide sleeve to the CRDM housingfurther comprises releasing the compression of the compressible guidesleeve to retainably couple to the CRDM housing.

Example 4

The method of any one of Examples 2-3, wherein the compressible guidesleeve comprises a multiple leaf compressible flex sections, whereineach of the multiple leaf compressible flex sections comprises a flange.The method comprises compressing the multiple leaf compressible flexsections to contract the flanges prior to inserting the compressed guidesleeve into the guide funnel, and releasing the compression of thecompressible guide sleeve after insertion into the CRDM housing torelease the flanges to engage a counterbore ledge defined by the CRDMhousing.

Example 5

The method of any one of Examples 1-4, comprising performing a finalgauging of the alignment of the extension tube.

Example 6

The method of any one of Examples 2-5, wherein the compressible guidesleeve is inserted into the guide funnel from a position below thereactor vessel head.

Example 7

The method of any one of Examples 1-6, wherein the extension tube isinstalled from a position below the reactor vessel head.

Example 8

The method of any one of Examples 1-7, wherein prior to aligning theextension tube with the threaded end of the head penetration nozzle andthreading the threaded end of the extension tube to the threaded end ofthe threaded head penetration nozzle, the method comprises joining athreaded adapter to the threaded end of the threaded head penetrationnozzle, wherein the threaded adapter comprises male threads sized andconfigured to threadably couple to the threaded end of the extensiontube.

Example 9

A method for installing an extension tube in a nuclear reactorcomprising a control rod drive mechanism (CRDM) housing with anon-threaded head penetration nozzle and a thermal sleeve disposedtherein. The method comprises machining the non-threaded CRDM housing,installing and aligning a threaded adapter to the machined end of thenon-threaded CRDM housing, joining the threaded adapter to the machinedend of the non-threaded CRDM housing, machining a bore defined by thenon-threaded CRDM housing, machining a bore defined by the threadedadapter, machining an outside diameter of the joint between the machinedend of the non-threaded CRDM housing and the threaded adapter,installing an extension tube to the threaded adapter, and installingretention fillets welds between the extension tube and the threadedadapter.

Example 10

The method of Example 9, wherein machining the non-threaded CRDM housingcomprises preparing a face of the non-threaded CRDM housing, andturning-back an inside diameter of the bore defined by the non-threadedCRDM housing.

Example 11

The method of any one of Examples 9-10, wherein joining the threadedadapter to the machined end of the non-threaded CRDM housing comprisesperforming a penetration welding technique to form the joint.

Example 12

The method of any one of Examples 9-11, wherein joining the threadedadapter to the machined end of the non-threaded CRDM housing comprisesperforming a full penetration welding technique to form the joint.

Example 13

The method of any one of Examples 9-12, wherein installing an extensiontube to the threaded adapter comprises threading the extension tube onthe threaded adapter, and torqueing the extension tube on the threadedadapter.

Example 14

The method of any one of Examples 9-13, comprising gauging the alignmentof the extension tube relative to the threaded head penetration nozzle.

Example 15

The method of any one of Examples 9-14, comprising installing a guidefunnel to the non-threaded end of the extension tube.

Example 16

The method of any one of Examples 9-15, comprising installing acompressible guide sleeve to the non-threaded CRDM housing.

Example 17

The method of Example 16, wherein installing the compressible guidesleeve to the non-threaded CRDM housing comprises compressing thecompressible guide sleeve, and inserting the compressed guide sleevethrough the extension tube, the head penetration nozzle, and thenon-threaded CRDM housing. Installing the compressible guide sleeve tothe non-threaded CRDM housing further comprises releasing thecompression of the compressible guide sleeve to retainably couple to thenon-threaded CRDM housing.

Example 18

The method of any one of Examples 16-17, wherein the compressible guidesleeve comprises a multiple leaf compressible flex sections, whereineach of the multiple leaf compressible flex sections comprises a flange.The method comprises compressing the multiple leaf compressible flexsections to contract the flanges prior to inserting the compressed guidesleeve into the extension tube, and releasing the compression of thecompressible guide sleeve after insertion into the non-threaded CRDMhousing to release the flanges to engage a counterbore ledge defined bythe non-threaded CRDM housing.

Example 19

The method of any one of Examples 9-18, comprising performing a finalgauging of the alignment of the extension tube.

Example 20

The method of any one of Examples 16-19, wherein the compressible guidesleeve is inserted into the guide funnel from a position below thereactor vessel head.

Example 21

The method of any one of Examples 9-20, wherein the extension tube isinstalled from a position below the reactor vessel head.

1-8. (canceled)
 9. A method for installing an extension tube in anuclear reactor comprising a control rod drive mechanism (CRDM) housingwith a non-threaded head penetration nozzle and a thermal sleevedisposed therein, the method comprising: machining the non-threaded CRDMhousing; installing and aligning a threaded adapter to the machined endof the non-threaded CRDM housing; joining the threaded adapter to themachined end of the non-threaded CRDM housing; machining a bore definedby the non-threaded CRDM housing; machining a bore defined by thethreaded adapter; machining an outside diameter of the joint between themachined end of the non-threaded CRDM housing and the threaded adapter;installing an extension tube to the threaded adapter; and installingretention fillets welds between the extension tube and the threadedadapter.
 10. The method of claim 9, wherein machining the non-threadedCRDM housing comprises: preparing a face of the non-threaded CRDMhousing; and turning-back an inside diameter of the bore defined by thenon-threaded CRDM housing.
 11. The method of claim 9, wherein joiningthe threaded adapter to the machined end of the non-threaded CRDMhousing comprises performing a penetration welding technique to form thejoint.
 12. The method of claim 11, wherein joining the threaded adapterto the machined end of the non-threaded CRDM housing comprisesperforming a full penetration welding technique to form the joint. 13.The method of claim 9, wherein installing an extension tube to thethreaded adapter comprises: threading the extension tube on the threadedadapter; and torqueing the extension tube on the threaded adapter. 14.The method of claim 9, comprising gauging the alignment of the extensiontube relative to the threaded head penetration nozzle.
 15. The method ofclaim 9, comprising installing a guide funnel to the non-threaded end ofthe extension tube.
 16. The method of claim 9, comprising installing acompressible guide sleeve to the non-threaded CRDM housing.
 17. Themethod of claim 16, wherein installing the compressible guide sleeve tothe non-threaded CRDM housing comprises: compressing the compressibleguide sleeve; inserting the compressed guide sleeve through theextension tube, the head penetration nozzle, and the non-threaded CRDMhousing; and releasing the compression of the compressible guide sleeveto retainably couple to the non-threaded CRDM housing.
 18. The method ofclaim 17, wherein the compressible guide sleeve comprises a multipleleaf compressible flex sections, wherein each of the multiple leafcompressible flex sections comprises a flange, the method comprising:compressing the multiple leaf compressible flex sections to contract theflanges prior to inserting the compressed guide sleeve into theextension tube; and releasing the compression of the compressible guidesleeve after insertion into the non-threaded CRDM housing to release theflanges to engage a counterbore ledge defined by the non-threaded CRDMhousing.
 19. The method of claim 18, comprising performing a finalgauging of the alignment of the extension tube.
 20. The method of claim19, wherein the compressible guide sleeve is inserted into the guidefunnel from a position below the reactor vessel head.
 21. The method ofclaim 9, wherein the extension tube is installed from a position belowthe reactor vessel head.